One of the means for fastening an object to the surface of another object which has been conventionally used is a method of using surface fasteners. In this method, a male surface fastener having hook fastener elements is fixed onto the surface of one object and a female surface fastener having loop fastener elements is fixed onto the surface of the other object. By overlaying one surface fastener to the other and engaging both fastener elements with each other, one object is fixed to the surface of the other object. Various surface fasteners made of different materials, for example, a fabric surface fastener, and employing different fastening systems have been used.
A combination of fabric surface fasteners, for example, a combination of a hook surface fastener (A) having hook fastener elements formed by monofilaments on a base fabric and a loop surface fastener (B) having loop fastener elements formed by multifilaments which are capable of engaging with the hook fastener elements on a base fabric have been widely known. The fabric surface fasteners are sold in a bag with both types of surface fasteners being engaged with each other and widely used in many fields, for example, clothes, shoes, headwear, belts, supporters, pillow covers, bags, sphygmomanometers, other miscellaneous daily goods, binding tapes, package materials, civil engineering and construction materials, and agriculture and fishery materials, and toys.
A mixed hook/loop surface fastener wherein the hook fastener elements and the loop fastener elements are mixedly formed in the same surface of a base fabric is also known. Compared with the conventional fastening device which needs two separate surface fasteners wherein one has hook fastener elements and the other has loop fastener element, the mixed hook/loop surface fastener needs only one type of surface fastener for fastening and the demand for it has been recently increased.
Each of the hook surface fastener (A) and the loop surface fastener (B) are generally produced by forming each of the hook fastener elements and the loop fastener elements at the time a base fabric comprising ground warp yarns and ground weft yarns is produced. Namely, the hook surface fastener (A) is produced by feeding monofilaments for forming the hook fastener elements into the base fabric in parallel to the ground warp yarns, projecting the monofilaments from the base fabric at intervals so as to form loops, heat-setting the loops, and then cutting loops at one leg to form the hook fastener elements. The loop surface fastener (B) is produced by feeding multifilaments for forming loop fastener elements into the base fabric in parallel to the ground warp yarns and projecting the multifilaments from the base fabric at intervals in a form of loops to form the loop fastener elements.
As the ground warp yarn, the ground weft yarn, the monofilament for the hook fastener element, and the multifilament for the loop fastener element, which are main components of the hook surface fastener (A) and the loop surface fastener (B), fibers formed from a polyamide polymer, such as nylon 6, nylon 66, and nylon 610, or a copolymer mainly based thereon have been generally used. However, a base fabric employing a polyamide fiber changes its shape and, in some cases, loses its shape by waving due to water and moisture absorption. Therefore, the polyamide fiber has significant disadvantages of impairing the quality and high-grade appearance of the product to which a surface fastener is attached and not necessarily providing a high engagement strength, which is the most important property required for the surface fastener.
These days, clothes are mainly fabricated from polyester fiber. When a surface fastener made of polyamide is attached to polyester clothes, polyamide and polyester are difficult to dye under the same dyeing condition due to the significant difference in their dyeabilities. Therefore, a large number of surface fasteners with various color shades which match the colors of the final products should be stored to assure uniform color shades between polyamide and polyester.
To eliminate the disadvantage in the use of polyamide fiber, the use of a fiber formed from a polyester polymer such as a low water and moisture absorbing polyethylene terephthalate or polybutylene terephthalate and a copolymer mainly based thereon has been considered recently. Some documents actually report the use of polyester fiber for the surface fastener.
For example, Patent Document 1 reports, in addition to the use of a synthetic fiber formed from a polyamide polymer such as nylon 6, nylon 66 and nylon 610, a synthetic fiber formed from a polyester polymer such as polyethylene terephthalate, polybutylene terephthalate and a copolymer mainly based thereon is usable as the fiber for forming the fastener element of surface fastener and a knitted woven fabric for carrying the fastener elements.
Patent Document 2 teaches to form the base fabric of surface fastener from, in addition to a fiber formed from polyamide such as nylon 6 and nylon 66, a fiber formed from polyester such as polyethylene terephthalate and polybutylene terephthalate. The document further teaches that a monofilament of nylon or polyester is preferred for the hook fastener element, and a multifilament of nylon or polyester is preferred for the loop fastener element.
The inventors had studied the surface fastener made by using a polyester fiber, i.e., the main fiber for clothes in these days, which is free from the significant disadvantage of waving due to water and moisture absorption found in the surface fastener made of a polyamide fiber. As a result, the inventors have found that the loop fastener element made of a multifilament of polyethylene terephthalate-based polyester had the disadvantage of failing to provide a high engagement strength, because the multifilament which form the loop was hardly separated into individual filaments. In addition, the surface fastener was hard in touch and not necessarily suitable for the application requiring a soft touch, such as clothes and daily necessities. It has been further found that the hook fastener element made of a monofilament of polybutylene terephthalate-based polyester failed to provide a sufficient engagement strength, because the hook fastener element engaged with the loop yarn was easily deformed and disengaged from the loop yarn by a small pulling force.
To prevent, the hook fastener elements and the loop fastener elements from being pulled out of the base fabric by a force for disengagement, the resistance to pull-out has been enhanced in a conventional technique by applying an adhesive (back coat resin) to the back surface of the base fabric to anchor the yarns which form the fastener elements to the base fabric. However, since the adhesive makes the base fabric hard and stiff, the resultant product is not suitable for use in clothing applications which require flexibility. In another known technique (Patent Document 3), the resistance to pull-out is enhanced by using a heat fusible fiber as the fiber for forming the surface fastener, and fusing the fibers for forming the fastener element to fusion-bond the fused fibers to the base fabric. When polyamide fibers are used as the fiber for forming the base fabric, the fiber performance is significantly reduced by the thermal fusion bonding, because the polyamide fibers are poor in heat resistance.
Since the hook surface fastener and the loop surface fastener are manufactured by the same maker, the surface fastener commercially available includes the hook fastener elements and the loop fastener elements, both made from the same resin. For example, when the hook fastener elements are made of nylon 6 monofilaments, the cooperating loop fastener elements are made of nylon 6 multifilaments. When the hook fastener elements are made of polyethylene terephthalate monofilaments, the cooperating loop fastener elements are made of polyethylene terephthalate multifilaments.
The reason for the above may be because the hook surface fastener and the loop surface fastener are manufactured by the same maker; and the hook surface fastener and the loop surface fastener are attached to the same object, and therefore the same dyeability is required for the hook surface fastener and the loop surface fastener. In addition, the engagement strength of surface fastener can be varied freely to some extent by changing the fineness of the monofilament for forming the hook fastener elements, the number of filaments in the multifilament for forming the loop fastener elements, and the fastener element density per unit area. The above reasons may have led a skilled person away from using a monofilament for forming hook fastener elements and a multifilament for forming loop fastener elements which are made from different resins.
Patent Document 4 describes a mixed hook/loop surface fastener having, on the same surface of the base fabric, the hook fastener elements with 1.3 to 3.8 mm height and the loop fastener elements with 1.5 to 4 mm height which is higher than that of the hook fastener elements by 0.2 to 2 mm. The document teaches that fibers of a thermoplastic resin, such as polyamide, polyester, polypropylene, and polyethylene, are usable as the fibers for forming the hook fastener elements and the loop fastener elements.
Patent Document 5 describes a mixed hook/loop surface fastener having the hook fastener elements and the loop fastener elements on the same base fabric, wherein the engagement is not formed by a small load, but formed only by applying a large load. The document teaches that synthetic fibers, such as polyamide fiber, polyester fiber, and polyolefin fiber, are usable as the fibers for forming the hook fastener elements and the loop fastener elements, with fibers of polyamide such as nylon-6 and nylon-66 and fibers of polyester such as polyethylene terephthalate and polybutylene terephthalate being preferred.
However, these patent documents merely describe in their working examples that polyester fibers are used for forming the hook fastener elements and the loop fastener elements and that the hook fastener elements are formed by polyester monofilaments and the loop fastener elements are formed by nylon-66 multifilaments.
The inventors have studied a mixed surface fastener in which the hook fastener elements and the loop fastener elements are both made of polyethylene terephthalate-based fibers and have found that each multifilament which forms the loop fastener elements is difficult to separate into individual filaments to prevent the hook fastener elements from entering into the loops of the loop fastener elements, thereby failing to obtain a sufficient engagement strength. The inventors have further found that a sufficient engagement strength cannot be obtained also in a mixed surface fastener in which the hook fastener elements and the loop fastener elements are both made of polybutylene terephthalate-based fibers, because the hook fastener elements are excessively soft. It has been further found that a sufficient engagement strength cannot be obtained even when trying to increase the engagement strength by forming the hook fastener elements from monofilaments having a larger fineness, because the hook fastener elements are difficult to enter into the loop fastener elements.
It has been further found that a surface fastener wherein the hook fastener elements or the loop fastener elements are formed of nylon fibers is poor in the dimension stability to humidity and waves when absorbing water. In the conventional technique, to prevent the hook fastener elements and the loop fastener element from being pulled out of the surface fastener during disengagement, an adhesive is applied to the back surface of the base fabric to enhance the resistance to pull-out of the fastener elements. However, the base fabric becomes hard and stiff by applying an adhesive to the back surface of the base fabric, and the obtained product is not suitable for use in clothing applications which require flexibility. In another known technique to enhance the resistance to pull-out of the fastener elements, a heat fusible fiber is used for forming the surface fastener, and the fibers which form the fastener elements are fusion-bonded to the fused fibers in the base fabric (Patent Document 3). When polyamide fibers are used as the fiber for forming the base fabric, the fiber performance is significantly reduced by the thermal fusion bonding because the polyamide fibers are poor in heat resistance.    Patent Document 1: JP 2002-238621A    Patent Document 2: JP 2002-223817A    Patent Document 3: WO 2005/122817    Patent Document 4: JP 5-154009A    Patent Document 5: JP 2003-125813A